a) Field of the Invention
The invention is directed to an arrangement and a method for detecting coatings lying on surfaces of structural component parts and for determining the characteristics thereof, in particular of coatings of water, ice and dirt on surfaces, preferably in structural components parts of vehicles. Above all, the chemical characteristics and surface properties of the coatings, particularly the roughness, are to be determined.
b) Description of the Related Art
In order to detect such coatings on surfaces of vehicle parts of this type and to determine their characteristics, these coatings are usually irradiated or penetrated by optical radiation and the radiation which is reflected by these coatings or which passes through them is measured and evaluated in different spectral regions. The presence of coatings can be deduced from these measurements and when such coatings are present their characteristics, particularly their chemical properties, can be determined.
There are various methods and arrangements for determining the surface condition of structural component parts in vehicles.
DE 199 27 015 A1 discloses a method and a device for determining the thickness and growth rate of a coating of ice on structural component parts of aircraft, wherein the radiation impinging on a coating on the surface of the structural component part is resolved into wavelength regions by a holographic grating connected to a photoelectric line receiver and the line receiver compares the measured radiation to a stored reflection curve of the surface of the structural component part without coating. The growth rate of a coating of this kind can also be determined within a number of temporally spaced measurement intervals.
The device for carrying out the measurements has a window through which the radiation which is influenced by the surface reaches the grating via an optical imaging system and a completely illuminated entrance slit, is spectrally separated according to wavelength on the grating, and is imaged on the line receiver by the grating. The signals of the elements of the line receiver are evaluated by means of a controlling and evaluating unit which is connected to the line receiver. The results of the measurements are made visible by a display.
This method is disadvantageous due to the fact that no distinction is made between the mechanical states of these coatings. Only a sum thickness or concentration is determined. In particular, coatings of ice, snow or frost cannot be distinguished spectrographically or, if so, only in a highly uneconomical manner. The roughness of a coating cannot be determined in this way.
FR 2 810 732 A1 discloses a spectrometer with a two-dimensional detector. The signal of a plurality of detector elements which lie perpendicular to the dispersion direction of the spectrometer and which are associated with the same wavelength are summed in the two-dimensional detectors. The spectrum obtained is evaluated. CCD elements or CMOS elements are provided as detector elements.